Camera modules (imaging apparatuses) that make white balance adjustments in accordance with a color temperature of a light source have been widely used. Without white balance adjustments, for example, an object under a fluorescent lamp may be taken in a greenish state or an object under an incandescent lamp may be taken in a reddish state. A camera module attempts to take a white portion of an object in a white state close to nature through white balance adjustments. An automatic white balance control (AWB) system is a system that automatically makes white balance adjustments.
The AWB system sets a color temperature range in which the white balance should be judged to a color judgment gate. By setting the range tinged with a color by light from a light source, though originally achromatic, for white balance adjustments, the color judgment gate can distinguish between an originally achromatic portion and a chromatic portion regardless of the color temperature of the light source. The AWB system integrates a signal level of pixels sorted by the color judgment gate for one frame and dividing the integrated value by the sorted number of pixels to calculate an average value per pixel in the frame. If the integrated data is a color difference signal, the AWB system adjusts the white balance so that the signal level of pixels sorted by the color judgment gate becomes zero.
A camera module using a single image sensor may cause a phenomenon in which a color that is originally not present appears, that is, a false color viewed in the light of the structure of the image sensor. The image sensor does not identify the color itself and thus picks up the additive primaries (or the subtractive primaries) by color separation using a color filter. If the color is not separated and not recognized correctly, a false color is generated in principle. A false color is more likely to appear particularly in an edge portion, color boundaries, and boundaries of light and shade of an object image. A false color may have high saturation or may be close to achromatic and contained in a color temperature range sorted by the color judgment gate. Therefore, a conventional AWB system has a problem that the accuracy of white balance adjustments is decreased by pixels of false color components close to achromatic being included for integration targets of white balance adjustments. Particularly when an object with less achromatic portions is taken, the white balance may be adjusted to a point that significantly deviates from an ideal point by almost all pixels to be integration targets being occupied by false color components.